The invention relates to fuzing means, and in particular to electronic fuzing means for munitions. Specifically, the invention relates to an electronic fuzing means for munitions that can be reprogrammed without disassembly of the munitions to replace parts that would be destroyed by programming methods of the prior art.
In the prior art various means have been used to arm a munition during the launching or deployment operation. Such arming means, however, involved the destruction of internal parts, or otherwise causing internal changes, that required disassembly of the unit to replace the parts if it had to be reprogrammed. Several of the problems in the prior art are discussed hereinafter. In general, there are two methods in the prior art of electrically programming a non-volatile memory of munition fuzes. The first method burns out a fuseable link providing non-alterable single bit data storage. The second method requires energy on the memory element while it is being altered (programmed).
One of the means of the prior art for arming a munition electrically was to induce a short high frequency pulse by electromagnetic coupling into the munition's internal arming circuitry. Usually, the high frequency pulse had to have sufficient energy to burn out fuseable wire links (which then programmed) and actuated the munition. Frequently, the programming was accomplished by controlling the amplitude of the high frequency pulse. However, due to the limited resolution of such systems the number of instructions were limited to only two.
Another problem with some of the prior art arming devices was that they frequently attempted to combine the programming and the activation operations during the launch period. The combined operations during launch limited the time available to deliver programming instructions and usually prevented any last minute change in setting.
Still another problem in the prior art devices was that the energy transferred by electro-magnetic coupling could not be delivered accurately, because of varying mechanical tolerances and differences in the properties of the magnetic materials surrounding and bridging the inductive working gap.
Yet another problem with the prior art devices using wire links for fuzing was the fact that the link burn out action follows an exponential curve requiring precisely defined amounts of energy to be delivered to the links for consistent results.
The combination of limited time for programming variations in mechanical tolerances and magnetic properties, and the need for precisely defined amounts of energy tended to produce an arming system during launch which was unreliable.
U.S. Pat. No. 4,160,416 details a programmed self-destruct system to solve the aforementioned problems, however, the system is cumbersome and introduces other problems. The resulting problems are because the system utilizes memory devices that require power to be programmed. This requires the programming process to be a two-pass process: the first to power up a capacitor to act as a battery; and the second to transmit data. This adds great complexity to the munitions circuitry where space is a premium. In addition, bubble memories have a far greater ability and are more insensitive to external stimuli than other forms of electronic data storage.
Regarding the aforementioned United States Patent, of the prior art, it is further to be noted that the bubble memory of the present invention is not substitutable in the aforementioned patent, nor is it an obvious matter to one skilled in the art of munition fuzing or to one in utilizing bubble memories. The field is relatively new and new technologies for bubble memories are being developed that are not mere obvious substitutions.
Bubble memories require signals with a relatively high peak current not normally available in electronic circuitry. Therefore, bubble memories are sold as systems that include (for the purpose of making their presence transparent to the user) a "current pulse driver" and a "coil predriver" and "drive transistors" to develop the required currents. In addition, bubble memories are typically used as mass memory devices. When used in this way speed of writing and reading data is of primary importance. This dictates the design of the bubble memory device as well as the ancillary system components. Standard bubble memory devices are typically encoded in an active state to reduce the required number of package pins and time required for encoding. These constraints are not applicable to the fuzing problem, thus opening up a new application area for bubble memories.